Although the iPhone 4S isn't yet available, a number of enthusiasts were able to give it a test run at Apple's event on Tuesday. And they've now written their initial impressions. They generally praise the greater speed, higher quality camera, and the effectiveness of Siri. TiPb has posted a roundup of several of these reviews. Be sure to read the review on This Is My Next, which says that Siri, the new speech recognition feature, is indeed impressive.